=head2 Wildcard expansion
File specifications containing wildcards are allowed both on
-the command line and within Perl globs (e.g. <CE<lt>*.cE<gt>>). If
+the command line and within Perl globs (e.g. <CE<lt>*.cE<gt>>). If
the wildcard filespec uses VMS syntax, the resultant
filespecs will follow VMS syntax; if a Unix-style filespec is
passed in, Unix-style filespecs will be returned.
+In both cases, VMS wildcard expansion is performed. (csh-style
+wildcard expansion is available if you use C<File::Glob::glob>.)
If the wildcard filespec contains a device or directory
specification, then the resultant filespecs will also contain
a device and directory; otherwise, device and directory
You may also use backticks to invoke a DCL subprocess, whose
output is used as the return value of the expression. The
-string between the backticks is passed directly to lib$spawn
-as the command to execute. In this case, Perl will wait for
-the subprocess to complete before continuing.
+string between the backticks is handled as if it were the
+argument to the C<system> operator (see below). In this case,
+Perl will wait for the subprocess to complete before continuing.
=head1 PERL5LIB and PERLLIB
If the call to C<exec> does not follow a call to C<fork>, it
will cause Perl to exit, and to invoke the command given as
an argument to C<exec> via C<lib$do_command>. If the argument
-begins with a '$' (other than as part of a filespec), then it
+begins with '@' or '$' (other than as part of a filespec), then it
is executed as a DCL command. Otherwise, the first token on
the command line is treated as the filespec of an image to
run, and an attempt is made to invoke it (using F<.Exe> and
the process defaults to expand the filespec) and pass the
-rest of C<exec>'s argument to it as parameters.
+rest of C<exec>'s argument to it as parameters. If the token
+has no file type, and matches a file with null type, then an
+attempt is made to determine whether the file is an executable
+image which should be invoked using C<MCR> or a text file which
+should be passed to DCL as a command procedure.
You can use C<exec> in both ways within the same script, as
long as you call C<fork> and C<exec> in pairs. Perl
The C<system> operator creates a subprocess, and passes its
arguments to the subprocess for execution as a DCL command.
Since the subprocess is created directly via C<lib$spawn()>, any
-valid DCL command string may be specified. If LIST consists
-of the empty string, C<system> spawns an interactive DCL subprocess,
-in the same fashion as typiing B<SPAWN> at the DCL prompt.
+valid DCL command string may be specified. If the string begins with
+'@', it is treated as a DCL command unconditionally. Otherwise, if
+the first token contains a character used as a delimiter in file
+specification (e.g. C<:> or C<]>), an attempt is made to expand it
+using a default type of F<.Exe> and the process defaults, and if
+successful, the resulting file is invoked via C<MCR>. This allows you
+to invoke an image directly simply by passing the file specification
+to C<system>, a common Unixish idiom. If the token has no file type,
+and matches a file with null type, then an attempt is made to
+determine whether the file is an executable image which should be
+invoked using C<MCR> or a text file which should be passed to DCL
+as a command procedure.
+
+If LIST consists of the empty string, C<system> spawns an
+interactive DCL subprocess, in the same fashion as typiing
+B<SPAWN> at the DCL prompt.
+
Perl waits for the subprocess to complete before continuing
execution in the current process. As described in L<perlfunc>,
the return value of C<system> is a fake "status" which follows
is found, rather than a CLI symbol or CRTL C<environ> element with
the same name.
-When an element of C<%ENV> is set to a non-empty string, the
+When an element of C<%ENV> is set to a defined string, the
corresponding definition is made in the location to which the
first translation of F<PERL_ENV_TABLES> points. If this causes a
logical name to be created, it is defined in supervisor mode.
+(The same is done if an existing logical name was defined in
+executive or kernel mode; an existing user or supervisor mode
+logical name is reset to the new value.) If the value is an empty
+string, the logical name's translation is defined as a single NUL
+(ASCII 00) character, since a logical name cannot translate to a
+zero-length string. (This restriction does not apply to CLI symbols
+or CRTL C<environ> values; they are set to the empty string.)
An element of the CRTL C<environ> array can be set only if your
copy of Perl knows about the CRTL's C<setenv()> function. (This is
present only in some versions of the DECCRTL; check C<$Config{d_setenv}>
to see whether your copy of Perl was built with a CRTL that has this
function.)
-When an element of C<%ENV> is set to an empty string or C<undef>,
+When an element of C<%ENV> is set to C<undef>,
the element is looked up as if it were being read, and if it is
found, it is deleted. (An item "deleted" from the CRTL C<environ>
array is set to the empty string; this can only be done if your
but after the element is deleted, another attempt is made to
look up the element, so an inner-mode logical name or a name in
another location will replace the logical name just deleted.
-It is not possible at present to define a search list logical name
-via %ENV.
+In either case, only the first value found searching PERL_ENV_TABLES
+is altered. It is not possible at present to define a search list
+logical name via %ENV.
The element C<$ENV{DEFAULT}> is special: when read, it returns
Perl's current default device and directory, and when set, it
=head2 SDBM_File
-SDBM_File works peroperly on VMS. It has, however, one minor
-difference. The database directory file created has a L<.sdbm_dir>
-extension rather than a L<.dir> extension. L<.dir> files are VMS filesystem
+SDBM_File works properly on VMS. It has, however, one minor
+difference. The database directory file created has a F<.sdbm_dir>
+extension rather than a F<.dir> extension. F<.dir> files are VMS filesystem
directory files, and using them for other purposes could cause unacceptable
problems.
=head1 Revision date
-This document was last updated on 26-Feb-1998, for Perl 5,
-patchlevel 5.
+This document was last updated on 26-Feb-2000, for Perl 5,
+patchlevel 6.
=head1 AUTHOR
-Charles Bailey bailey@cor.newman.upenn.edu
-
-Last revision by Dan Sugalski sugalskd@ous.edu
+Charles Bailey <bailey@cor.newman.upenn.edu>
+Dan Sugalski <dan@sidhe.org>
projects / p5sagit/p5-mst-13.2.git / blobdiff